Concentration-measurement device and concentration-measurement method

ABSTRACT

A concentration measurement apparatus measures a temporal relative change amount (ΔcHb, ΔO 2 Hb) of either or both of total hemoglobin concentration and oxygenated hemoglobin concentration in the head that vary due to repetition of chest compression, and includes a light incidence section making measurement light incident on the head, a light detection section detecting the measurement light propagated through the interior of the head and generating a detection signal in accordance with the intensity of the measurement light, and a CPU determining, based on the detection signal, the relative change amount (ΔcHb, ΔO 2 Hb) and performing a filtering process of removing frequency components less than a predetermined frequency from frequency components contained in the relative change amount (ΔcHb, ΔO 2 Hb).

TECHNICAL FIELD

The present invention relates to a concentration measurement apparatusand a concentration measurement method.

BACKGROUND ART

An example of a device for noninvasively measuring hemoglobinconcentration information inside a living body is described in PatentDocument 1. With this device, light is made incident inside the livingbody, and thereafter, light scattered inside the living body is detectedby each of a plurality of photodiodes. Then, based on the intensities ofthe detected light components, a rate of change of the detected lightamount in the direction of distance from the light incidence point iscalculated. Hemoglobin oxygen saturation is calculated based on apredetermined relationship of the rate of change of the detected lightamount and the light absorption coefficient. Also, based on apredetermined relationship of the temporal change of the rate of changeof the detected light amount and the temporal change of the lightabsorption coefficient, respective concentration changes of oxygenatedhemoglobin (O₂Hb), deoxygenated hemoglobin (HHb), and total hemoglobin(cHb) are calculated.

CITATION LIST Patent Literature

-   Patent Document 1: Japanese Patent Application Laid-Open No.    H7-255709

Non Patent Literature

-   Non-Patent Document 1: Susumu Suzuki et al., “Tissue oxygenation    monitor using NIR spatially resolved spectroscopy,” Proceedings of    SPIE 3597, pp. 582-592

SUMMARY OF INVENTION Technical Problem

The primary patients in the emergency medical field in recent years arethose suffering cardiopulmonary arrest outside a hospital. The number ofout-of-hospital cardiopulmonary arrest persons exceeds 100 thousand peryear, and emergency medical care of these persons is a major socialdemand. An essential procedure for out-of-hospital cardiopulmonaryarrest persons is chest compression performed in combination withartificial respiration. Chest compression is an act where the lower halfof the sternum is cyclically compressed by another person's hands toapply an artificial pulse to the arrested heart. A primary object ofchest compression is to supply blood oxygen to the brain of thecardiopulmonary arrest person. Whether or not chest compression is beingperformed appropriately thus has a large influence on the life or deathof the cardiopulmonary arrest person. Methods and devices that areuseful for objectively judging whether or not chest compression is beingperformed appropriately are thus being demanded.

The present invention has been made in view of the above situation, andan object thereof is to provide a concentration measurement apparatusand a concentration measurement method that enable objective judgment ofwhether or not chest compression is being performed appropriately.

Solution to Problem

In order to solve the above-described problem, a concentrationmeasurement apparatus according to the present invention is aconcentration measurement apparatus measuring a temporal relative changeamount of at least one of total hemoglobin concentration and oxygenatedhemoglobin concentration in the head that vary due to repetition ofchest compression, and includes a light incidence section makingmeasurement light incident on the head, a light detection sectiondetecting the measurement light that has propagated through the interiorof the head and generating a detection signal in accordance with anintensity of the measurement light, and a calculation sectiondetermining, based on the detection signal, the temporal relative changeamount of at least one of the total hemoglobin concentration and theoxygenated hemoglobin concentration, and performing a filtering processof removing frequency components less than a predetermined frequencyfrom frequency components contained in the relative change amount.

Further, a concentration measurement method according to the presentinvention is a concentration measurement method of measuring a temporalrelative change amount of at least one of total hemoglobin concentrationand oxygenated hemoglobin concentration in the head that vary due torepetition of chest compression, and includes a light incidence step ofmaking measurement light incident on the head, a light detection step ofdetecting the measurement light that has propagated through the interiorof the head and generating a detection signal in accordance with anintensity of the measurement light, and a calculation step ofdetermining, based on the detection signal, the temporal relative changeamount of at least one of the total hemoglobin concentration and theoxygenated hemoglobin concentration, and performing a filtering processof removing frequency components less than a predetermined frequencyfrom frequency components contained in the relative change amount.

The present inventors used a concentration measurement apparatus usingnear-infrared light to measure relative change amounts of totalhemoglobin concentration and oxygenated hemoglobin concentration in thehead at a frequency sufficiently higher than the heartbeat frequency. Asa result, the present inventors found that, in chest compression,certain changes occur in the total hemoglobin concentration and theoxygenated hemoglobin concentration of the interior of the head (thatis, the brain) each time the sternum is compressed cyclically. Thisphenomenon is considered to be due to increase of blood flow within thebrain by the chest compression, and may be usable as a material forobjectively judging whether or not chest compression is being performedappropriately. However, the amplitude (for example, of approximately 1μmol) of such a concentration change due to chest compression isextremely small in comparison to the amplitudes (normally of not lessthan several μmol) of changes of even longer cycle that occur in anormally active state of a healthy person or in a state where variousprocedures are being performed on a cardiopulmonary arrest person. It isthus extremely difficult to observe the variations due to chestcompression if simply values corresponding to the total hemoglobinconcentration and the oxygenated hemoglobin concentration are measured.

Therefore, with the above-described concentration measurement apparatusand concentration measurement method, in addition to determining thetemporal relative change amount of either or both of the totalhemoglobin concentration and the oxygenated hemoglobin concentration,the frequency components less than the predetermined frequency areremoved from the frequency components contained in the relative changeamount in the calculation section or the calculation step. Normally, thecycle of concentration changes due to chest compression (that is, thepreferable compression cycle in the chest compression process) isshorter than the cycles of the primary concentration changes in thestate where various procedures are being performed on a cardiopulmonaryarrest person. Therefore, by removing the low frequency components (thatis, the long cycle components) from the measured relative change amountas in the above-described concentration measurement apparatus andconcentration measurement method, information on concentration changesdue to chest compression can be extracted favorably. Further, based onthis information, a performer can objectively judge whether or not thechest compression is being performed appropriately. It thus becomespossible for the performer to perform or maintain the chest compressionmore appropriately. Here, the “filtering process of removing frequencycomponents less than a predetermined frequency” in the above-describedconcentration measurement apparatus and the concentration measurementmethod refers to a process of decreasing the proportion of frequencycomponents less than the predetermined frequency until the frequencycomponent due to chest compression appears at a sufficientlyrecognizable level, and is not limited to completely removing thefrequency components less than the predetermined frequency.

Advantageous Effects of Invention

In accordance with the concentration measurement apparatus andconcentration measurement method according to the present invention,whether or not chest compression is being performed appropriately can bejudged objectively.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of a concentration measurement apparatusaccording to an embodiment.

FIG. 2 includes (a) a plan view of a configuration of a probe, and (b) asectional side view taken along line II-II of (a).

FIG. 3 is a block diagram of a configuration example of theconcentration measurement apparatus.

FIG. 4 is a flowchart of a concentration measurement method according toan embodiment.

FIG. 5 includes (a) a diagram of incidence timings of laser light beamsof wavelengths λ₁ to λ₃, and (b) a diagram of output timings of digitalsignals from an A/D converter circuit.

FIG. 6 is a graph of filter characteristics of a digital filter.

FIG. 7 is a graph of results of using the digital filter having thecharacteristics shown in FIG. 6 to remove frequency components less thana predetermined frequency from frequency components contained in atemporal relative change amount (ΔO₂Hb) of oxygenated hemoglobin tothereby extract a temporal variation component due to a spontaneousheartbeat that simulates the repetition of chest compression.

FIG. 8 is a graph of results of using a filtering process by smoothingto remove frequency components less than a predetermined frequency fromfrequency components contained in a temporal relative change amount(ΔcHb) of total hemoglobin to thereby extract a temporal variationcomponent due to a spontaneous heartbeat that simulates the repetitionof chest compression.

FIG. 9 shows diagrams for describing concepts of a filtering process bywhich maximal portions or minimal portions of a variation areuniformized.

FIG. 10 shows diagrams of examples of a display screen in a displaysection.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of a concentration measurement apparatus anda concentration measurement method according to the present inventionwill be described in detail with reference to the accompanying drawings.In the description of the drawings, elements that are the same areprovided with the same reference symbols, and redundant description isomitted.

FIG. 1 is a conceptual diagram of a concentration measurement apparatus1 according to an embodiment of the present invention. To provideinformation for objectively judging whether or not chest compression(arrow A in the figure) is being performed appropriately on acardiopulmonary arrest person 50, the concentration measurementapparatus 1 measures respective temporal variations (relative changeamounts) from initial amounts of total hemoglobin (cHb) concentration,oxygenated hemoglobin (O₂Hb) concentration, and deoxygenated hemoglobin(Mb) concentration of the head 51 that vary due to repeated chestcompression and displays the measurement results on a display section 15to notify a person performing the chest compression. The concentrationmeasurement apparatus 1 makes light beams of predetermined wavelengths(λ₁, λ₂, and λ₃) be incident on a predetermined light incidence positionfrom a probe 20 fixed to the head 51, and detects intensities of lightcomponents emitted from predetermined light detection positions on thehead 51 to examine the effects of the oxygenated hemoglobin (O₂Hb) andthe deoxygenated hemoglobin (HHb) on the light, and based thereon,repeatedly calculates the temporal relative change amounts of theoxygenated hemoglobin (O₂Hb) and the deoxygenated hemoglobin (HHb).Also, the apparatus applies a filtering process to time series data thatare the calculation results, and thereby removes low frequencycomponents to extract a short-cycle temporal variation component due tothe repetition of chest compression, and displays the temporal variationcomponent in a visible manner. As the light of predeterminedwavelengths, for example, near-infrared light is used.

(a) in FIG. 2 is a plan view of a configuration of a probe 20. (b) inFIG. 2 is a sectional side view taken along line II-II of (a) in FIG. 2.The probe 20 has a light incidence section 21 and a light detectionsection 22. The light incidence section 21 and the light detectionsection 22 are disposed with an interval, for example, of 5 cm from eachother, and are practically integrated by a holder 23 made of flexible,black silicone rubber. Here, the interval suffices to be not less thanapproximately 3 to 4 cm.

The light incidence section 21 includes an optical fiber 24 and a prism25, and has a structure that makes the measurement light, transmittedfrom a main unit section 10 of the concentration measurement apparatus1, incident substantially perpendicularly on the skin of the head. Themeasurement light is, for example, a laser light beam of pulse form, andis transmitted from the main unit section 10.

The light detection section 22 detects measurement light components thathave propagated through the interior of the head, and generatesdetection signals that are in accordance with the intensities of themeasurement light components. The light detection section 22 is, forexample, a one-dimensional photosensor having an array of Nphotodetection elements 26 aligned in a direction of distance from thelight incidence section 21. Also, the light detection section 22 furtherhas a pre-amplifier section 27 that integrates and amplifiesphotocurrents output from the photodetection elements 26. By thisarrangement, weak signals can be detected with high sensitivity togenerate detection signals, and the signals can be transmitted via acable 28 to the main unit section 10. Here, the light detection section22 may instead be a two-dimensional photosensor, or may be configured bya charge coupled device (CCD). The probe 20 is, for example, fixed by anadhesive tape or a stretchable band, etc., onto a forehead portionwithout hair.

FIG. 3 is a block diagram of a configuration example of theconcentration measurement apparatus 1. The concentration measurementapparatus 1 shown in FIG. 3 includes the main unit section 10 inaddition to the probe 20 described above. The main unit section 10includes a light emitting section (for example, a laser section) 11, asample hold circuit 12, an A/D converter circuit 13, a CPU 14, a displaysection 15, a ROM 16, a RAM 17, and a data bus 18.

The light emitting section 11 is configured by a laser diode and acircuit that drives the laser diode. The light emitting section 11 iselectrically connected to the data bus 18 and receives an instructionsignal for instructing the driving of the laser diode from the CPU 14that is likewise electrically connected to the data bus 18. Theinstruction signal contains information on the light intensity andwavelength (for example, a wavelength among wavelengths λ₁, λ₂, and λ₃)of the laser light output from the laser diode. The light emittingsection 11 drives the laser diode based on the instruction signalreceived from the CPU 14 and outputs laser light as measurement light tothe probe 20 via the optical fiber 24. Here, the light emitting elementof the light emitting section 11 does not have to be a laser diode, andsuffices to be an element that can successively output light beams of aplurality of wavelengths in the near-infrared region. Also, a lightemitting diode such as an LED that is built into the probe 20 may beused as the light incidence section 21.

The sample hold circuit 12 and the A/D converter circuit 13 input thedetection signals transmitted via the cable 28 from the probe 20 andperform holding and conversion of the signals to digital signals thatare then output to the CPU 14. The sample hold circuit 12 simultaneouslyholds the values of N detection signals. The sample hold circuit 12 iselectrically connected to the data bus 18, and receives a sample signal,indicating the timing of holding of the detection signals, from the CPU14 via the data bus 18. Upon receiving the sample signal, the samplehold circuit 12 simultaneously holds N detection signals input from theprobe 20. The sample hold circuit 12 is electrically connected to theA/D converter circuit 13, and outputs each of the held N detectionsignals to the A/D converter circuit 13.

The A/D converter circuit 13 is means for converting the detectionsignals from analog signals to digital signals. The A/D convertorcircuit 13 successively converts the N detection signals received fromthe sample hold circuit 12 into digital signals. The A/D convertorcircuit 13 is electrically connected to the data bus 18, and outputs theconverted detection signals to the CPU 14 via the data bus 18.

The CPU 14 is a calculation section in the present embodiment and, basedon the detection signals received from the A/D converter circuit 13,calculates the required amounts among the temporal relative changeamount (ΔO₂Hb) of the oxygenated hemoglobin concentration contained inthe interior of the head, the temporal relative change amount (ΔHHb) ofthe deoxygenated hemoglobin concentration, and the temporal relativechange amount (ΔcHb) of the total hemoglobin concentration, which is thesum of the above two concentrations. Further, the CPU 14 applies afiltering process to the temporal relative change amounts (ΔO₂Hb, ΔHHb,and ΔcHb) to remove frequency components less than a predeterminedfrequency from frequency components contained in the amounts to therebyextract a temporal variation component due to repetition of chestcompression. After performing such a process, the CPU 14 transmits theresults via the data bus 18 to the display section 15. Here, a method ofcalculating the temporal relative change amounts (ΔO₂Hb, ΔHHb, and ΔcHb)based on the detection signals and a method of the filtering processshall be described later. The display section 15 is electricallyconnected to the data bus 18, and displays the results transmitted fromthe CPU 14 via the data bus 18.

The operation of the concentration measurement apparatus 1 shall now bedescribed. In addition, the concentration measurement method accordingto the present embodiment shall be described. FIG. 4 is a flowchart ofthe concentration measurement method according to the presentembodiment.

First, the light emitting section 11 successively outputs the laserlight beams of wavelengths λ₁ to λ₃ based on the instruction signal fromthe CPU 14. The laser light beams (measurement light beams) propagatethrough the optical fiber 24, reach the light incidence position at theforehead portion, and enter inside the head from the light incidenceposition (light incidence step, S11). The laser light beam made to enterinside the head propagates while being scattered inside the head andbeing absorbed by measurement object components, and parts of the lightreach the light detection positions of the forehead portion. The laserlight components that reach the light detection positions are detectedby the N photodetection elements 26 (light detection step, S12). Eachphotodetection element 26 generates a photocurrent in accordance withthe intensity of the detected laser light component. These photocurrentsare converted into voltage signals (detection signals) by thepre-amplifier section 27, and the voltage signals are transmitted to andheld by the sample hold circuit 12 of the main unit section 10, andthereafter, converted to digital signals by the A/D converter circuit13.

Here, (a) in FIG. 5 is a diagram of incidence timings of the laser lightbeams of wavelengths λ₁ to λ₃, and (b) in FIG. 5 is a diagram of outputtimings of the digital signals from the A/D converter circuit 13. Asshown in FIG. 5, when the laser light of wavelength λ₁ is made incident,N digital signals D₁(1) to D₁(N) corresponding to the N photodetectionelements 26 are obtained sequentially. Next, when the laser light ofwavelength λ₂ is made incident, N digital signals D₂(1) to D₂(N)corresponding to the N photodetection elements 26 are obtainedsequentially. Thus, (3×N) digital signals D₁(1) to D₃(N) are output fromthe A/D converter circuit 13.

Subsequently, the calculation section 14 calculates the hemoglobinoxygen saturation (TOI) based on the digital signals D(1) to D(N). Also,the calculation section 14 uses at least one digital signal from thedigital signals D(1) to D(N) to calculate the temporal relative changeamount (ΔO₂Hb) of the oxygenated hemoglobin concentration, the temporalrelative change amount (ΔHHb) of the deoxygenated hemoglobinconcentration, and the temporal relative change amount (ΔcHb) of thetotal hemoglobin concentration, which is the sum of these (calculationstep, step S13). Then, of the frequency components contained in therelative change amounts (ΔcHb, ΔO₂Hb, and ΔHHb), the frequencycomponents less than the predetermined frequency are removed by afiltering process (calculation step, S14). The relative change amounts(ΔcHb, ΔO₂Hb, and ΔHHb) after the filtering process are displayed on thedisplay section 15 (step S15). In the concentration measurementapparatus 1 and the concentration measurement method according to thepresent embodiment, the above-described steps S11 to S15 are repeated.

The above-described calculation performed by the calculation section 14in the calculation steps S13 and S14 shall now be described in detail.

If D_(λ1)(T₀) to D_(λ3)(T₀) are values of the detection signals,respectively corresponding to the laser light wavelengths λ₁ to λ₃, at atime T₀ at a certain light detection position, and D_(λ1)(T₁)˜D_(λ3)(T₁)are likewise values at a time T₁, the change amounts of the detectedlight intensities in the time T₀ to T₁ are expressed by the followingformulas (1) to (3).

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack & \; \\{{\Delta\;{{OD}_{1}\left( T_{1} \right)}} = {\log\left( \frac{D_{\lambda\; 1}\left( T_{1} \right)}{D_{\lambda\; 1}\left( T_{0} \right)} \right)}} & (1) \\\left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack & \; \\{{\Delta\;{{OD}_{2}\left( T_{1} \right)}} = {\log\left( \frac{D_{\lambda\; 2}\left( T_{1} \right)}{D_{\lambda\; 2}\left( T_{0} \right)} \right)}} & (2) \\\left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack & \; \\{{\Delta\;{{OD}_{3}\left( T_{1} \right)}} = {\log\left( \frac{D_{\lambda\; 3}\left( T_{1} \right)}{D_{\lambda\; 3}\left( T_{0} \right)} \right)}} & (3)\end{matrix}$Here, in the formulas (1) to (3), ΔOD₁(T₁) is the temporal change amountof the detected light intensity of wavelength λ₁, ΔOD₂(T₁) is thetemporal change amount of the detected light intensity of wavelength λ₂,and ΔOD₃(T₁) is the temporal change amount of the detected lightintensity of wavelength λ₃.

Further, if ΔO₂Hb(T₁) and ΔHHb(T₁) are the temporal relative changeamounts of the concentrations of oxygenated hemoglobin and deoxygenatedhemoglobin, respectively, in the period from time T₀ to time T₁, thesecan be determined by the following formula (4).

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack & \; \\{\begin{pmatrix}{\Delta\; O_{2}{{Hb}\left( T_{1} \right)}} \\{\Delta\;{{HHb}\left( T_{1} \right)}}\end{pmatrix} = {\begin{pmatrix}a_{11} & a_{12} & a_{13} \\a_{21} & a_{22} & a_{23}\end{pmatrix}\begin{pmatrix}{\Delta\;{{OD}_{1}\left( T_{1} \right)}} \\{\Delta\;{{OD}_{2}\left( T_{1} \right)}} \\{\Delta\;{{OD}_{3}\left( T_{1} \right)}}\end{pmatrix}}} & (4)\end{matrix}$

Here, in the formula (4), the coefficients a11 to a23 are constantsdetermined from absorbance coefficients of O₂Hb and HHb for lightcomponents of wavelengths λ₁, λ₂, and λ₃. Also, the temporal relativechange amount ΔcHb(T₁) of the total hemoglobin concentration in the headcan be determined by the following formula (5).[Formula 5]ΔcHb(T ₁)=ΔO₂Hb(T ₁)+ΔHHb(T ₁)  (5)

The CPU 14 performs the above calculation on detection signals from oneposition among the N light detection positions to calculate therespective temporal relative change amounts (ΔO₂Hb, ΔHHb, and ΔcHb) ofthe oxygenated hemoglobin concentration, deoxygenated hemoglobinconcentration, and total hemoglobin concentration. Further, the CPU 14performs, for example, any of the following filtering processes on thetemporal relative change amounts (ΔO₂Hb, ΔHHb, and ΔcHb) that have thusbeen calculated.

(1) Filtering Process by a Digital Filter

Let X(n) be a data string related to a temporal relative change amount(ΔO₂Hb, ΔHHb, or ΔcHb) obtained at a predetermined cycle. Here, n is aninteger. By multiplying the respective data of the data string X(n) by,for example, the following filter coefficients A(n), with n=0 being thetime center, an acyclic linear phase digital filter is realized.

A(0)=¾

A(3)=A(−3)=−⅙

A(6)=A(−6)=−⅛

A(9)=A(−9)=− 1/12

To describe in further detail, a delay operator for the data string X(n)is represented by the following formula (6). Here, f is the timefrequency (units: 1/sec). Also, ω is the angular frequency, and ω=2πf. Tis the cycle at which the data string X(n) is obtained, and is set, forexample, to a cycle of 1/20 seconds for measuring a variation waveformat approximately 150 times per minute (2.5 Hz).[Formula 6]e ^(jωnT)=COS(ωnT)+j SIN(ωnT)e ^(−jωnT)=COS(ωnT)−j SIN(ωnT)  (6)In this case, the digital filter characteristics when theabove-described filter coefficients A(n) are used are described by thefollowing formula (7).

$\begin{matrix}{\mspace{79mu}\left\lbrack {{Formula}\mspace{14mu} 7} \right\rbrack} & \; \\{{R(\omega)} = {{\frac{3}{4} - {\frac{1}{6}\left( {{\mathbb{e}}^{{- 3}{j\omega}\; T} + {\mathbb{e}}^{{+ 3}{j\omega}\; T}} \right)} - {\frac{1}{8}\left( {{\mathbb{e}}^{{- 6}{j\omega}\; T} + {\mathbb{e}}^{{+ 6}{j\omega}\; T}} \right)} - {\frac{1}{12}\left( {{\mathbb{e}}^{{- 9}{j\omega}\; T} + {\mathbb{e}}^{{+ 9}{j\omega}\; T}} \right)}} = {\frac{3}{4} - {\frac{1}{3}{{COS}\left( {3\omega\; T} \right)}} - {\frac{1}{4}{{COS}\left( {6\omega\; T} \right)}} - {\frac{1}{6}{{COS}\left( {9\omega\; T} \right)}}}}} & (7)\end{matrix}$The digital filter is thus expressed by a product-sum operation of thedata string X(n) and the corresponding coefficients. Further, byconverting the time frequency f in formula (7) to a time frequency F perminute (units: 1/min), the following formula (8) is obtained.

$\begin{matrix}\left\lbrack {{Formula}\mspace{14mu} 8} \right\rbrack & \; \\{{R(F)} = {\frac{3}{4} - {\frac{1}{3}{{COS}\left( {\frac{3\pi}{600}F} \right)}} - {\frac{1}{4}{{COS}\left( {\frac{6\pi}{600}F} \right)}} - {\frac{1}{6}{{COS}\left( {\frac{9\pi}{600}F} \right)}}}} & (8)\end{matrix}$

FIG. 6 is a graph of R(F), and shows the filter characteristics of thedigital filter. In FIG. 6, the horizontal axis represents the number ofheartbeats per minute, and the vertical axis represents the value ofR(F). Further, FIG. 7 is a graph of results of using the digital filtershown in FIG. 6 to remove (reduce) frequency components less than thepredetermined frequency from the frequency components contained in thetemporal relative change amount (ΔO₂Hb) of oxygenated hemoglobin toextract a temporal variation component due to a spontaneous heartbeatthat simulates the repetition of chest compression. In FIG. 7, a graphG31 represents the relative change amount (ΔO₂Hb) before the filteringprocess, a graph G32 represents the long cycle components (frequencycomponents less than the predetermined frequency) contained in therelative change amount (ΔO₂Hb) before the filtering process, and a graphG33 represents the relative change amount (ΔO₂Hb) after the filteringprocess. As shown in FIG. 7, by the above digital filter, the temporalvariation component due to the spontaneous heartbeat or the repetitionof chest compression can be extracted favorably.

(2) Filtering Process by a Smoothing Calculation (Least Square ErrorCurve Fitting)

A least square error curve fitting using a high-order function (forexample, a fourth-order function) is performed on a data string X(n),within the above-described data string X(n), that is obtained in apredetermined time (for example, 3 seconds, corresponding to 5 beats)before and after n=0 as the time center. The constant term of thehigh-order function obtained is then deemed to be a smoothed component(frequency component less than the predetermined frequency) at n=0. Thatis, by subtracting the smoothed frequency component from the originaldata X(0), the frequency component less than the predetermined frequencycan be removed from the frequency components contained in the relativechange amount to separate/extract the temporal variation component dueto repeated chest compression.

FIG. 8 is a graph of results of using such a filtering process to remove(reduce) frequency components less than the predetermined frequency fromthe frequency components contained in the temporal relative changeamount (ΔcHb) of the total hemoglobin to extract a temporal variationcomponent due to a spontaneous heartbeat that simulates the repetitionof chest compression. In FIG. 8, a graph G41 represents the relativechange amount (ΔcHb) before the filtering process, a graph G42represents the long cycle components (frequency components less than thepredetermined frequency) contained in the relative change amount (ΔcHb)before the filtering process, a graph G43 represents the relative changeamount (ΔcHb) after the filtering process, and a graph G44 indicates the5-second average amplitudes in the relative change amount (ΔcHb) afterthe filtering process. As shown in FIG. 8, by the filtering process bythe above-described smoothing calculation, the temporal variationcomponent due to the spontaneous heartbeat or the repetition of chestcompression can be extracted favorably.

(3) Filtering Process of Uniformizing the Maximal Portions or MinimalPortions of Variation

(a) in FIG. 9 and (b) in FIG. 9 are diagrams for describing the conceptsof the present filtering process. In this filtering process, forexample, the maximal values in the temporal variation of the relativechange amount (ΔO₂Hb, ΔHHb, or ΔcHb) are determined, and by deeming themaximal values P1 in the temporal variation graph G51 to be of fixedvalue as shown in (a) in FIG. 9, the frequency components less than thepredetermined frequency that are contained in the relative change amount(ΔO₂Hb, ΔHHb, or ΔcHb) are removed. Or, for example, the minimal valuesin the temporal variation of the relative change amount (ΔO₂Hb, ΔHHb, orΔcHb) are determined, and by deeming the minimal values P2 in thetemporal variation graph G51 to be of fixed value as shown in (b) inFIG. 9, the frequency components less than the predetermined frequencythat are contained in the relative change amount (ΔO₂Hb, ΔHHb, or ΔcHb)are removed. By thus making either or both the maximal values P1 andminimal values P2 closer to fixed values, the temporal variationcomponent due to the repetition of chest compression can be extractedfavorably.

The effects of the concentration measurement apparatus 1 and theconcentration measurement method according to the present embodimentwith the above arrangements shall now be described. In view of theproblem to be solved described above, present inventors used aconcentration measurement apparatus using near-infrared light to measurethe relative change amounts (ΔcHb and ΔO₂Hb) of the total hemoglobinconcentration and the oxygenated hemoglobin concentration in the head ata frequency sufficiently higher than the heartbeat frequency. As aresult, the present inventors found that, in chest compression, certainchanges occur in the total hemoglobin concentration and the oxygenatedhemoglobin concentration of the interior of the head (that is, thebrain) each time the sternum is compressed cyclically. This phenomenonis considered to be due to increase of blood flow within the brain bythe chest compression, and may be usable as information for objectivelyjudging whether or not chest compression is being performedappropriately. However, the amplitude (for example, of approximately 1μmol) of such a concentration change due to chest compression isextremely small in comparison to the amplitudes (normally of not lessthan several μmol) of changes of even longer cycle that occur in anormally active state of a healthy person or in a state where variousprocedures are being performed on a cardiopulmonary arrest person. It isthus extremely difficult to observe the variations due to chestcompression if simply values corresponding to the total hemoglobinconcentration and the oxygenated hemoglobin concentration are measured.

Therefore, in the concentration measurement apparatus 1 and theconcentration measurement method according to the present embodiment, inaddition to the CPU 14 determining the temporal relative change amounts(ΔcHb, ΔO₂Hb, and ΔHHb) of the total hemoglobin concentration, theoxygenated hemoglobin concentration, and the deoxygenated hemoglobinconcentration in the calculation step S13, the frequency components lessthan the predetermined frequency are removed from the frequencycomponents contained in the relative change amounts (ΔcHb, ΔO₂Hb, andΔHHb). Normally, the cycle of concentration changes due to chestcompression (that is, the preferable compression cycle of the chestcompression process) is shorter than the cycles of the primaryconcentration changes in the state where various procedures are beingperformed on a cardiopulmonary arrest person. Therefore, by removing thelow frequency components (that is, the long cycle components) from themeasured relative change amounts (ΔcHb, ΔO₂Hb, and ΔHHb) as in theconcentration measurement apparatus 1 and the concentration measurementmethod according to the present embodiment, information on theconcentration changes due to chest compression can be extractedfavorably. Further, based on this information, a performer canobjectively judge whether or not the chest compression is beingperformed appropriately. It thus becomes possible for the performer toperform or maintain the chest compression more appropriately.

Here, in the present embodiment, the “filtering process of removingfrequency components less than a predetermined frequency” refers to aprocess of decreasing the proportion of frequency components less thanthe predetermined frequency until the frequency component due to chestcompression appears at a sufficiently recognizable level, and is notrestricted to completely removing the frequency components less than thepredetermined frequency.

Also, the calculation cycle of the relative change amounts (ΔcHb, ΔO₂Hb,and ΔHHb) is preferably not more than 0.2 seconds (not less than 5 Hz ascalculation frequency). A favorable cycle of chest compression isgenerally said to be not less than approximately 100 times per minute(that is, once every 0.6 seconds). If the calculation cycle of therelative change amount is not more than one-third of the chestcompression cycle, the concentration changes due to the chestcompression can be detected favorably.

Further, in the filtering process described above, the frequencycomponents less than the predetermined frequency are removed from thefrequency components contained in the relative change amounts (ΔcHb,ΔO₂Hb, and ΔHHb) to extract the temporal variation component due to therepetition of sternal compression. The predetermined frequency ispreferably not more than 1.66 Hz. Information on the concentrationchanges due to the not less than approximately 100 times per minute ofchest compression can thereby be extracted favorably.

Here, a screen display on the display section 15 shall now be described.(a) in FIG. 10 and (b) in FIG. 10 are examples of a display screen onthe display section 15. In the display screen shown in (a) in FIG. 10,the temporal relative change amount (ΔO₂Hb) of the oxygenated hemoglobinconcentration after the filtering process and the temporal relativechange amount (ΔHHb) of the deoxygenated hemoglobin concentration afterthe filtering process are displayed respectively as individual graphsG11 and G12. In one example, the horizontal axis of the graphs G11 andG12 represents time, and the vertical axis represents the change amount.

Further, in the display screen shown in (b) in FIG. 10, a graph G21representing the temporal relative change amount (ΔcHb) of the totalhemoglobin concentration after the filtering process is displayed, andfurther, a region B22 of the amplitude of the graph G21 that is taken upby the temporal relative change amount (ΔO₂Hb) of the oxygenatedhemoglobin concentration, and a region B23 taken up by the temporalrelative change amount (ΔHHb) of the deoxygenated hemoglobinconcentration are displayed in a color-coded manner. In one example, thehorizontal axis of the graph G21 represents time, and the vertical axisrepresents the change amount. By thus displaying the region B22 and theregion B23 in a color-coded manner, the chest compression performer canrefer to the displayed information to visually and intuitively recognizethe proportion of oxygenated hemoglobin in the blood delivered to thehead, and thereby rapidly judge the need for artificial respiration.

The display section 15 may also display information (first information)of numerical values, etc., related to a ratio (A2/A1) of the amplitude(the amplitude A1 shown in (b) in FIG. 10) of the temporal variation ofthe temporal relative change amount (ΔcHb) of the total hemoglobinconcentration and the amplitude (A2 shown in (b) in FIG. 10) of thetemporal variation of the temporal relative change amount (ΔO₂Hb) of theoxygenated hemoglobin concentration. Or, the display section 15 maydisplay information (second information) of numerical values, etc.,related to a ratio (I2/I1) of the integrated value I1 (the sum of theareas of the region B22 and the region B23 shown in (b) in FIG. 10) ofthe temporal variation of the temporal relative change amount (ΔcHb) ofthe total hemoglobin concentration and the integrated value I2 (the areaof the region B22 shown in (b) in FIG. 10) of the temporal variation ofthe temporal relative change amount (ΔO₂Hb) of the oxygenated hemoglobinconcentration. By displaying either or both of the above, the chestcompression performer can refer to the displayed information to know theproportion of oxygenated hemoglobin in the blood delivered to the head,and thereby favorably judge the need for artificial respiration. Here,the above information is calculated by the CPU 14 and transmitted to thedisplay section 15. Further, the above information may be average valuesfor a predetermined time (for example, 5 seconds).

Further, the CPU 14 may issue a warning to the chest compressionperformer, when the calculated value of the ratio (A2/A1) or ratio(I2/I1) is less than a predetermined threshold value (for example, 90%).The chest compression performer can thereby be more reliably notified ofthe lowering of the proportion of oxygenated hemoglobin in the blooddelivered to the head. As a method for such warning, for example, anoutput of a warning sound or an indication of a warning display on thedisplay section 15 is preferable.

Also, the display section 15 may display information (third information)related to variation frequencies of the temporal relative change amounts(ΔcHb and ΔO₂Hb) of either or both of the total hemoglobin concentrationand the oxygenated hemoglobin concentration after the filtering processhas been performed. The performer can thereby be notified of the currentfrequency (cycle) of chest compression, and urged to make it approach anappropriate frequency (cycle), for example, of 100 times per minute.Here, the above information is calculated by the CPU 14 and transmittedto the display section 15. Further, the above information may be anaverage value for a predetermined time (for example, 5 seconds).

Also, the display section 15 may display the numerical value of theamplitude (A1 shown in (b) in FIG. 10) of the temporal variation of thetemporal relative change amount of the total hemoglobin concentration.The chest compression performer can thereby refer to the displayednumerical values to know the blood amount delivered into the brain, andthereby favorably judge whether or not the strength of chest compressionis sufficient. Here, the above numerical value may be an average valuefor a predetermined time (for example, 5 seconds). Further, the mainunit section 10 may also output a sound (for example, a simulated pulsesound such as blip, blip) each time the numerical value of the amplitudeis not less than a predetermined value. The performer can thereby benotified more reliably of whether or not an appropriate blood amount isbeing delivered into the brain.

The concentration measurement apparatus and the concentrationmeasurement method according to the present invention are not limited tothe embodiment described above, and various modifications are possible.For example, although with the concentration measurement apparatus 1 andthe concentration measurement method according to the above-describedembodiment, the respective relative change amounts (ΔcHb, ΔO₂Hb, andΔHHb) of the total hemoglobin concentration, oxygenated hemoglobinconcentration, and deoxygenated hemoglobin concentration are determined,with the concentration measurement apparatus and concentrationmeasurement method according to the present invention, information formaking an objective judgment of whether or not chest compression isbeing performed appropriately can be indicated by determining at leastone of the respective relative change amounts (ΔcHb and ΔO₂Hb) of thetotal hemoglobin concentration and oxygenated hemoglobin concentration.

Also, the filtering process in the concentration measurement apparatusand concentration measurement method according to the present inventionis not limited to those given as examples in regard to the embodiment,and any filtering process capable of removing frequency components lessthan a predetermined frequency from the relative change amounts (ΔcHband ΔO₂Hb) may be used favorably in the present invention.

Also with the present invention, the hemoglobin oxygen saturation (TOI),determined by near-infrared spectroscopic analysis in a manner similarto the respective relative change amounts (ΔcHb, ΔO₂Hb, and ΔHHb) of thetotal hemoglobin concentration, oxygenated hemoglobin concentration, anddeoxygenated hemoglobin concentration, may be displayed in a graph or asa numerical value together with the relative change amounts on thedisplay section. Improvement of the brain oxygen state by the chestcompression can thereby be confirmed to maintain the motivation of theperformer. The TOI may be an average value for a predetermined time (forexample, 5 seconds).

In the concentration measurement apparatus according to theabove-described embodiment, a configuration of a concentrationmeasurement apparatus measuring a temporal relative change amount of atleast one of total hemoglobin concentration and oxygenated hemoglobinconcentration in the head that vary due to repetition of sternalcompression, and including a light incidence section making measurementlight incident on the head, a light detection section detecting themeasurement light that has propagated through the interior of the headand generating a detection signal in accordance with the intensity ofthe measurement light, and a calculation section determining, based onthe detection signal, the temporal relative change amount of at leastone of the total hemoglobin concentration and the oxygenated hemoglobinconcentration, and performing a filtering process of removing frequencycomponents less than a predetermined frequency from frequency componentscontained in the relative change amount, is used.

Further, in the concentration measurement method according to theabove-described embodiment, a configuration of a concentrationmeasurement method of measuring a temporal relative change amount of atleast one of total hemoglobin concentration and oxygenated hemoglobinconcentration in the head that vary due to repetition of sternalcompression, and including a light incidence step of making measurementlight incident on the head, a light detection step of detecting themeasurement light that has propagated through the interior of the headand generating a detection signal in accordance with the intensity ofthe measurement light, and a calculation step of determining, based onthe detection signal, the temporal relative change amount of at leastone of the total hemoglobin concentration and the oxygenated hemoglobinconcentration, and performing a filtering process of removing frequencycomponents less than a predetermined frequency from frequency componentscontained in the relative change amount, is used.

The concentration measurement apparatus and the concentrationmeasurement method may be of a configuration where a calculation cycleof the relative change amount is not more than 0.2 seconds. A favorablecycle of chest compression is generally said to be not less thanapproximately 100 times per minute (that is, once every 0.6 seconds). Ifthe calculation cycle of the relative change amount is not more thanone-third of the chest compression cycle, the concentration changes dueto the chest compression can be detected. That is, by the calculationcycle of the relative change amount being not more than 0.2 seconds, theconcentration change due to the chest compression can be detectedfavorably.

Further, the concentration measurement apparatus and the concentrationmeasurement method may be of a configuration where the predeterminedfrequency is not more than 1.66 Hz. Information on the concentrationchanges due to the chest compression can thereby be extracted favorably.

Further, the concentration measurement apparatus may be of aconfiguration that further includes a display section displaying thecalculation result by the calculation section, and where the calculationsection determines the temporal relative change amount of the totalhemoglobin concentration and the temporal relative change amount of theoxygenated hemoglobin concentration, and determines first informationrelated to a ratio (A2/A1) of an amplitude (A1) of the temporalvariation of the temporal relative change amount of the total hemoglobinconcentration and an amplitude (A2) of the temporal variation of thetemporal relative change amount of the oxygenated hemoglobinconcentration, after the filtering process, and the display sectiondisplays the first information. Similarly, the concentration measurementmethod may be of a configuration where, in the calculation step, thetemporal relative change amount of the total hemoglobin concentrationand the temporal relative change amount of the oxygenated hemoglobinconcentration are determined, first information related to a ratio(A2/A1) of an amplitude (A1) of the temporal variation of the temporalrelative change amount of the total hemoglobin concentration and anamplitude (A2) of the temporal variation of the temporal relative changeamount of the oxygenated hemoglobin concentration, after the filteringprocess, is determined, and the first information is displayed. By theabove, the performer can refer to the displayed first information toknow the proportion of oxygenated hemoglobin in the blood delivered intothe brain, and thereby favorably judge the need for artificialrespiration.

Further, the concentration measurement apparatus may be of aconfiguration where the calculation section performs at least one of anoutput of a warning sound and an indication of a warning display on thedisplay section when the ratio (A2/A1) is less than a predeterminedthreshold. Similarly, the concentration measurement method may be of aconfiguration where at least one of an output of a warning sound and awarning display is performed when the ratio (A2/A1) is less than apredetermined threshold in the calculation step. The performer canthereby be more reliably notified of the lowering of the proportion ofoxygenated hemoglobin in the blood delivered into the brain.

Further, the concentration measurement apparatus may be of aconfiguration that further includes a display section displaying thecalculation result by the calculation section, and where the calculationsection determines the temporal relative change amount of the totalhemoglobin concentration and the temporal relative change amount of theoxygenated hemoglobin concentration, and determines at least one of anintegrated value (I1) of the temporal variation of the temporal relativechange amount of the total hemoglobin concentration and an integratedvalue (I2) of the temporal variation of the temporal relative changeamount of the oxygenated hemoglobin concentration, after the filteringprocess, and the display section displays at least one of the integratedvalue (I1) and the integrated value (I2). Similarly, the concentrationmeasurement method may be of a configuration where, in the calculationstep, the temporal relative change amount of the total hemoglobinconcentration and the temporal relative change amount of the oxygenatedhemoglobin concentration are determined, at least one of an integratedvalue (I1) of the temporal variation of the temporal relative changeamount of the total hemoglobin concentration and an integrated value(I2) of the temporal variation of the temporal relative change amount ofthe oxygenated hemoglobin concentration, after the filtering process, isdetermined, and at least one of the integrated value (I1) and theintegrated value (I2) is displayed. The performer can thereby refer tothe displayed values to judge whether or not the strength of chestcompression is sufficient.

Further, the concentration measurement apparatus may be of aconfiguration where the calculation section determines both theintegrated value (I1) and the integrated value (I2), and thereafter,further determines second information related to a ratio (I2/I1) of theintegrated value (I1) and the integrated value (I2), and the displaysection further displays the second information. Similarly, theconcentration measurement method may be of a configuration where, in thecalculation step, both of the integrated value (I1) and the integratedvalue (I2) are determined, second information related to a ratio (I2/I1)of the integrated value (I1) and the integrated value (I2) is furtherdetermined thereafter, and the second information is further displayed.The performer can thereby refer to the displayed second information toknow the proportion of oxygenated hemoglobin in the blood delivered intothe brain, and favorably judge the need for artificial respiration.

Further, the concentration measurement apparatus may be of aconfiguration where the calculation section performs at least one of anoutput of a warning sound and an indication of a warning display on thedisplay section when the ratio (I2/I1) is less than a predeterminedthreshold. Similarly, the concentration measurement method may be of aconfiguration where at least one of an output of a warning sound and awarning display is performed when the ratio (I2/I1) is less than apredetermined threshold in the calculation step. The performer canthereby be more reliably notified of the lowering of the proportion ofoxygenated hemoglobin in the blood delivered into the brain.

Further, the concentration measurement apparatus may be of aconfiguration that further includes a display section displaying thecalculation result by the calculation section, and where the calculationsection determines an amplitude (A1) of the temporal variation of thetemporal relative change amount of the total hemoglobin concentrationafter the filtering process, and the display section displays thenumerical value of the amplitude (A1). Similarly, the concentrationmeasurement method may be of a configuration where, in the calculationstep, an amplitude (A1) of the temporal variation of the temporalrelative change amount of the total hemoglobin concentration after thefiltering process is determined, and the numerical value of theamplitude (A1) is displayed. The performer can thereby refer to thedisplayed numerical value to know the blood amount delivered into thebrain, and thereby favorably judge whether or not the strength of chestcompression is sufficient.

Further, the concentration measurement apparatus may be of aconfiguration where the calculation section performs an output of asound each time the numerical value of the amplitude (A1) is not lessthan a predetermined value. Similarly, the concentration measurementmethod may be of a configuration where a sound is output each time thenumerical value of the amplitude (A1) is not less than a predeterminedvalue in the calculation step. The performer can thereby be morereliably notified that the blood amount being delivered into the brainis insufficient.

Further, the concentration measurement apparatus may be of aconfiguration that further includes a display section displaying thecalculation result by the calculation section, and where the calculationsection determines the temporal relative change amount of the totalhemoglobin concentration and the temporal relative change amount of theoxygenated hemoglobin concentration, and the display section displaysgraphs of the temporal relative change amount of the oxygenatedhemoglobin concentration and the temporal relative change amount of thedeoxygenated hemoglobin concentration contained in the total hemoglobinconcentration, after the filtering process, in a color-coded manner.Similarly, the concentration measurement method may be of aconfiguration where, in the calculation step, the temporal relativechange amount of the total hemoglobin concentration and the temporalrelative change amount of the oxygenated hemoglobin concentration aredetermined, and graphs of the temporal relative change amount of theoxygenated hemoglobin concentration and the temporal relative changeamount of the deoxygenated hemoglobin concentration contained in thetotal hemoglobin concentration, after the filtering process, aredisplayed in a color-coded manner. The performer can thereby refer tothe displayed information to visually and intuitively recognize theproportion of oxygenated hemoglobin in the blood delivered into thebrain, and thereby more rapidly judge the need for artificialrespiration.

Further, the concentration measurement apparatus may be of aconfiguration that further includes a display section displaying thecalculation result by the calculation section, and where the calculationsection calculates third information related to a variation frequency ofthe relative change amount after the filtering process, and the displaysection displays the third information. Similarly, the concentrationmeasurement method may be of a configuration where, in the calculationstep, third information related to a variation frequency of the relativechange amount after the filtering process is calculated, and the thirdinformation is displayed. The performer can thereby be notified of thecurrent frequency (cycle) of chest compression, and urged to make itapproach the appropriate frequency (cycle).

Further, the concentration measurement apparatus may be of aconfiguration where the calculation section removes the frequencycomponents less than the predetermined frequency from the frequencycomponents contained in the relative change amount by a digital filter.Similarly, the concentration measurement method may be of aconfiguration where, in the calculation step, the frequency componentsless than the predetermined frequency are removed from the frequencycomponents contained in the temporal relative change amount by a digitalfilter. Long cycle components can thereby be removed favorably from themeasured relative change amount, and information related to theconcentration changes due to chest compression can be extracted withhigh precision.

Further, the concentration measurement apparatus may be of aconfiguration where the calculation section calculates data resultingfrom smoothing of the temporal variation of the relative change amount,and subtracts the data from the relative change amount to remove thefrequency components less than the predetermined frequency from thefrequency components contained in the relative change amount. Similarly,the concentration measurement method may be of a configuration where, inthe calculation step, data resulting from smoothing of the temporalvariation of the temporal relative change amount are calculated, and thedata are subtracted from the temporal relative change amount to removethe frequency components less than the predetermined frequency from thefrequency components contained in the temporal relative change amount.Long cycle components can thereby be removed favorably from the measuredrelative change amount, and information related to the concentrationchanges due to chest compression can be extracted with high precision.

Further, the concentration measurement apparatus may be of aconfiguration where the calculation section determines at least one of amaximal value and a minimal value in the temporal variation of therelative change amount, and removes the frequency components less thanthe predetermined frequency from the frequency components contained inthe relative change amount based on at least one of the maximal valueand the minimal value. Similarly, the concentration measurement methodmay be of a configuration where, in the calculation step, at least oneof a maximal value and a minimal value in the temporal variation of thetemporal relative change amount is determined, and the frequencycomponents less than the predetermined frequency are removed from thefrequency components contained in the temporal relative change amountbased on at least one of the maximal value and the minimal value. Longcycle components can thereby be removed favorably from the measuredrelative change amount, and information related to the concentrationchanges due to chest compression can be extracted with high precision.

INDUSTRIAL APPLICABILITY

The present invention can be used as a concentration measurementapparatus and a concentration measurement method that enable objectivejudgment of whether or not chest compression is being performedappropriately.

REFERENCE SIGNS LIST

-   -   1—concentration measurement apparatus, 10—main unit section,        11—light emitting section, 12—sample hold circuit, 13—converter        circuit, 14—calculation section, 15—display section, 16—ROM,        17—RAM, 18—data bus, 20—probe, 21—light incidence section,        22—light detection section, 23—holder, 24—optical fiber,        25—prism, 26—photodetection element, 27—pre-amplifier section,        28—cable, 50—cardiopulmonary arrest person, 51—head, P1—maximal        value, P2—minimal value.

The invention claimed is:
 1. A concentration measurement apparatusmeasuring a temporal relative change amount of at least one of totalhemoglobin concentration, oxygenated hemoglobin concentration, anddeoxygenated hemoglobin concentration in the head that vary due torepetition of chest compression, comprising: a light source that makesmeasurement light having at least a first wavelength λ1 and a secondwavelength λ2 incident on the head; a light detector that detects themeasurement light that has propagated through the interior of the headand generating a first detection signal corresponding to the firstwavelength λ1 and a second detection signal corresponding to the secondwavelength λ2 in accordance with an intensity of the measurement light;and a processor electrically connected to the light detector andprogrammed to determine, based on the first detection signal and thesecond detection signal, the temporal relative change amount of at leastone of the total hethoglobin concentration (ΔcHb), the oxygenatedhemoglobin concentration (ΔO₂Hb), and the deoxygenated hemoglobinconcentration (ΔHHb), wherein the processor is programmed to perform afiltering process that removes frequency components less than apredetermined frequency of not more than 1.66 Hz to extract informationon the concentration change due to chest compression, and calculateinformation related to a variation frequency of the relative changeamount corresponding to a current frequency of chest compression, andwherein a calculation cycle of the relative change amount is not morethan 0.2 seconds.
 2. The concentration measurement apparatus accordingto claim 1, further comprising a display that displays the calculationresult obtained by the processor, and wherein the processor isprogrammed to determine the temporal relative change amount of the totalhemoglobin concentration and the temporal relative change amount of theoxygenated hemoglobin concentration, and determines first informationrelated to a ratio (A2/A1) of an amplitude (A1) of the temporalvariation of the temporal relative change amount of the total hemoglobinconcentration and an amplitude (A2) of the temporal variation of thetemporal relative change amount of the oxygenated hemoglobinconcentration, after the filtering process, and the display displays thefirst information.
 3. The concentration measurement apparatus accordingto claim 1, further comprising a display that displays the calculationresult obtained by the processor, and wherein the processor isprogrammed to determine the temporal relative change amount of the totalhemoglobin concentration and the temporal relative change amount of theoxygenated hemoglobin concentration, and determines at least one of anintegrated value (I1) of the temporal variation of the temporal relativechange amount of the total hemoglobin concentration and an integratedvalue (I2) of the temporal variation of the temporal relative changeamount of the oxygenated hemoglobin concentration, after the filteringprocess, and the display displays at least one of the integrated value(I1) and the integrated value (I2).
 4. The concentration measurementapparatus according to claim 3, wherein the processor is programmed todetermine both the integrated value (I1) and the integrated value (I2),and thereafter, further determines second information related to a ratio(I2/I1) of the integrated value (I1) and the integrated value (I2), andthe display displays the second information.
 5. The concentrationmeasurement apparatus according to claim 1, further comprising a displaythat displays the calculation result obtained by the processor, andwherein the processor is programmed to determine an amplitude (A1) ofthe temporal variation of the temporal relative change amount of thetotal hemoglobin concentration after the filtering process, and thedisplay displays the numerical value of the amplitude (A1).
 6. Theconcentration measurement apparatus according to claim 1, furthercomprising a display that displays the calculation result obtained bythe processor, and wherein the processor is programmed to determine thetemporal relative change amount of the total hemoglobin concentrationand the temporal relative change amount of the oxygenated hemoglobinconcentration, and the display displays graphs of the temporal relativechange amount of the oxygenated hemoglobin concentration and thetemporal relative change amount of the deoxygenated hemoglobinconcentration contained in the total hemoglobin concentration, after thefiltering process, in a color-coded manner.
 7. The concentrationmeasurement apparatus according to claim 1, wherein the processor isprogrammed to remove the frequency components less than thepredetermined frequency from the frequency components contained in therelative change amount by a digital filter.
 8. The concentrationmeasurement apparatus according to claim 1, wherein the processor isprogrammed to calculate data resulting from smoothing of the temporalvariation of the relative change amount, and subtracts the data from therelative change amount to remove the frequency components less than thepredetermined frequency from the frequency components contained in therelative change amount.
 9. The concentration measurement apparatusaccording to claim 1, wherein the processor is programmed to determineat least one of a maximal value and a minimal value in the temporalvariation of the relative change amount, and removes the frequencycomponents less than the predetermined frequency from the frequencycomponents contained in the relative change amount based on at least oneof the maximal value and the minimal value.
 10. The concentrationmeasurement apparatus according to claim 1, further comprising a displaythat displays the calculation result obtained by the processor, andwherein the display displays the information related to the variationfrequency.
 11. The concentration measurement apparatus according toclaim 1, further comprising a display that displays the calculationresult obtained by the processor, and wherein the processor calculateshemoglobin oxygen saturation, and the display displays the hemoglobinoxygen saturation.
 12. The concentration measurement apparatus accordingto claim 1, further comprising an A/D converter electrically connectedto the light detector and to the processor.
 13. A concentrationmeasurement method of measuring a temporal relative change amount of atleast one of total hemoglobin concentration, oxygenated hemoglobinconcentration, and deoxygenated hemoglobin concentration in the headthat vary due to repetition of chest compression, the method comprising:making measurement light having at least a first wavelength λ1 and asecond wavelength λ2, by a light source, incident on the head;detecting, by a light detector, the measurement light that haspropagated through the interior of the head and generating a firstdetection signal corresponding to the first wavelength λ1 and a seconddetection signal corresponding to the second wavelength λ2 in accordancewith an intensity of the measurement light; and determining, by aprocessor, based on the first detection signal and the second detectionsignal, the temporal relative change amount of at least one of the totalhemoglobin concentration (ΔcHb), the oxygenated hemoglobin concentration(ΔO₂Hb), and the deoxygenated hemoglobin concentration (ΔHHb), whereinthe processor is programmed to perform a filtering process that removesfrequency components less than a predetermined frequency of not morethan 1.66 Hz to extract information on the concentration change due tochest compression, and calculate information related to a variationfrequency of the relative change amount corresponding to a currentfrequency of chest compression, and wherein a calculation cycle of therelative change amount is not more than 0.2 seconds.